Nonlinear upconversion of solar-wind noise to higher frequencies

Determine whether solar-wind-induced forces on the LISA Pathfinder spacecraft couple nonlinearly to produce measurable acceleration noise at frequencies higher than those directly associated with solar-wind variability, beyond the direct linear couplings detectable by the methods used in this study.

Background

The analysis in this paper focuses on identifying linear correlations between solar-wind measurements from ACE and acceleration data from LISA Pathfinder (LPF). While the methods reliably detect direct, linear couplings, they do not exclude potential nonlinear mechanisms that could transfer low-frequency solar-wind variability into higher-frequency acceleration noise, including frequencies relevant to LISA’s observing band.

Clarifying whether such nonlinear upconversion occurs is important for bounding or characterizing potential spurious noise sources for both LPF and future LISA operations, especially if nonlinear processes could introduce coherence at higher frequencies despite minimal linear correlations.